76 University of Calif or nia Publicntions in Zoology [Vol. 16 



spindle is composed of faintly staining fibers, usually few in number, 

 formed inside the nuclear membrane. It is to be noted that the para- 

 desmose is outside the nuclear membrane and takes no part in the 

 formation of the spindle (pi. 9. figs. 7, 8). During this time also the 

 new flagella make their appearance as new outgrowths. 



With the appearance of the spindle fibers the chromatin becomes 

 massed into two large granules, which apparently split (pi. 9. fig. 7) 

 before taking a position on the spindle. The number of chromosomes 

 is two, as shown by numerous figures in the late anaphase and telophase 

 stages. In the equatorial plate the chromatin can very seldom be 

 resolved into individual chromosomes, but appears as undifferentiated 

 masse-s (pi. 9, figs. S, 9). Division is not always synchronous in both 

 nuclei, since one may lag somewhat behind the other (pi. 9, fig. 8). 



In the anaphase, as the chromosomes move towards the pole, inter- 

 zonal spindle fibers can still be seen stretched between the chromosomes 

 as well as connecting them with the blepharoplasts or centro.somes (pi. 9, 

 figs. 8, 9). The.se interzonal fibers later disappear (pi. 9, fig. 10) and 

 the only parts of the spindle remaining are the short fibers connecting 

 the centrosomes with the blepharoplasts. These become darker appar- 

 ently through chromatin moving out along them from the chromo- 

 somes (pi. 9, fig. 10). In the reorganization of the nucleus in the 

 telophase this migration of chromatin takes place to a greater extent, 

 the amount of chromatin becoming greater at the same time, until the 

 large, club-.shaped karyosome again appears (pi. 9. fig. 1) and the 

 nucleus is reconstituted. 



There is no con.striction and division of the nuclear membrane, but 

 instead this gradually fades out and disappears while two new mem- 

 branes are formed inside the old (pi. 9, figs. 10-12). The new mem- 

 brane, at its first appearance, is .stained but faintly, gradually be- 

 coming darker until, after the complete disappearance of the old 

 membrane, it takes a black color with iron haematoxylin (pi. 10, fig. 13). 

 The paradesmose persists throughout these stages, disappearing only 

 with the reorganization of the nuclcTis. 



Multiple Fission 



In common with most of the members of the Polymastigina, as 

 well perhaps as in the majority of Protozoa, it has been found that 

 multiple fission is prevalent among the Hexamitidae, though whether 

 preceded by conjugation, or not, is as yet undetermined. Its occur- 



